Myelodysplastic/Myeloproliferative Neoplasm, Unclassifiable (MDS/ MPN-UC) (also known as mixed myeloproliferative/ myelodysplastic syndrome, unclassifiable and overlap syndrome, unclassifiable) shows features of both myeloproliferative disease and myelodysplastic disease but does not meet the criteria for any of the other MDS/MPN entities.
Diagnostic criteria for MDS/MPN-UC can be either:
- The combination of four sets of criteria (a–d):
- Clinical, laboratory, and morphologic features of myelodysplastic syndrome (MDS) (e.g., refractory anemia, refractory anemia with ringed sideroblasts, refractory cytopenia with multilineage dysplasia, and refractory anemia with excess of blasts) with fewer than 20% blasts in the blood and bone marrow. (Refer to the PDQ summary on Fatigue for more information on anemia.)
- Prominent myeloproliferative features, e.g. platelet count greater than 600 × 109/L associated with megakaryocytic proliferation, or white blood cell count greater than 13.0 × 109/L with or without splenomegaly.
- No history of an underlying chronic myeloproliferative disorder (CMPD), MDS, or recent cytotoxic or growth factor therapy that could cause the myelodysplastic or myeloproliferative features.
- No Philadelphia chromosome or BCR/ABL fusion gene, del(5q), t(3;3)(q21;q26), or inv(3)(q21q26).
- Mixed myeloproliferative and myelodysplastic features that cannot be assigned to any other category of MDS, CMPD, or MDS/MPN.
Clinical characteristics of MDS/MPN-UC include the following:
- Features of both MDS and CMPD.
The incidence and etiology of MDS/MPN-UC are unknown.
Laboratory features typically include anemia and dimorphic erythrocytes on the peripheral blood smear. Thrombocytosis (platelet count >600 × 109/L) or leukocytosis (white blood cell count >13 × 109/L) are present. Neutrophils may exhibit dysplastic features, and giant or hypogranular platelets may be present. Blasts make up less than 20% of the white blood cells and of the nucleated cells of the bone marrow. The bone marrow is hypercellular and may exhibit proliferation in any or all of the myeloid lineages. Dysplastic features are present in at least one cell line.
No cytogenetic or molecular findings are available that are specific for MDS/MPN-UC. In one small series, six of nine patients (those with ringed sideroblasts associated with marked thrombocytosis [RARS-T]) showed a JAK2 V617F mutation causing constitutive activation of the JAK2 tyrosine kinase (a mutation also commonly observed in patients with polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis). Because of its rare occurrence, the prognosis and predictive factors are unknown.
Adult patients with MDS/MPN associated with platelet-derived growth factor receptor gene rearrangements are candidates for imatinib mesylate at standard dosages. Because of its rare occurrence, the literature only minimally addresses other treatment options for MDS/MPN-UC. Supportive care involves treating cytopenias and infection as necessary.
Current Clinical Trials
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with myelodysplastic/myeloproliferative neoplasm, unclassifiable. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.
- Orazi A, Germing U: The myelodysplastic/myeloproliferative neoplasms: myeloproliferative diseases with dysplastic features. Leukemia 22 (7): 1308-19, 2008. [PUBMED Abstract]
- Szpurka H, Tiu R, Murugesan G, et al.: Refractory anemia with ringed sideroblasts associated with marked thrombocytosis (RARS-T), another myeloproliferative condition characterized by JAK2 V617F mutation. Blood 108 (7): 2173-81, 2006. [PUBMED Abstract]
- U.S. Food and Drug Administration: FDA approves imatinib mesylate (Gleevec) as a single agent for the treatment of multiple indications. Rockville, Md: Food and Drug Administration, Center for Drug Evaluation and Research, Office of Oncology Drug Products (OODP), 2006. Available online. Last accessed February 07, 2012.